My compressor fridge runs at about 3A but it doesn’t run all the time, it cuts in and out, mostly out. Over 24 hours I reckon it uses 20Ah to 30Ah which is easily replaced by a B2B with an hour or two of driving. Also worth remembering that unlike a 3 way fridge the compressor only takes a few amps out of the available charge when driving.
I have paralleled B2Bs. The original Schaudt/Lippert WA121525 and a
Victron Orion XS 50. I have fitted a switch to the D+ feed to the WA121525 because it is not always needed and has only a very basic Li charging profile. The XS is a bit kinder to the
battery. When needed both run happily together.
Something I have done with my Ablemail B2Bs - and is possible with the Victrons as well, but not sure on other kit - is to vary the activation delays so they don't all come on (or go off) together.
My 60A B2B is actually a pair of 30A B2Bs in a single metal enclosure, so each half can be programmed independently. My 30A B2B is in it's own metal enclosure.
I have them set so there is a 5 second delay between each one turning on and also 5 seconds for each turning off - the idea is there is less of a sudden 'wham' on the alternator. I am happy enough with all the B2Bs active as the alternator is brand new. When it was the original c2007 one, I only used the third B2B when the voltage reached a higher level to avoid excess stress.
That's an impressively small unit considering it's rated at 50A. A couple of questions for the Blue Experts if they'd care to chip in:-
How long has that unit been out?
Any reported throttling back issues with it when it gets warm? (I know
Victron had this previously with a certain model, cant recall if it was a SCC or a B2B)
Lots of B2Bs seem to suffer from throttling back due to heat. The original Orion Smart-Tr B2B had this issue but a rework of the unit all but eliminated it (and
Victron offered a free swap-out for all the older units - an owner could quote the serial number and
Victron would know if it was in the affected period and so in scope for replacement)
The new Orion-XS is a very different product (as can be seen by the packaging) and I would guess
Victron learnt from their previous model what to change.
There are quite a few people that advocate setting the charge rate a little below the maximum so it will not not run at full power and so generate full heat. This is for the B2B and also the
Multiplus. I judge if that is worth doing by evaluating the install location... if very enclosed, then could be worth dropping to 90% of the rating.
On my B2Bs, they usually run upto 110% of the rated current (i can hit 100A charge on the 90A worth of B2B) and that is within spec as they are deliberately under quoted by the maker. I tested the 30A unit around 5 or 6 years ago and it output a constant 33A for 4 hours until it switched to absorption mode. But now they are in a much more enclosed area I added a fan that runs when the B2B is on to provide some airflow across the heatsinks - never hurts to cool electrics!
Does the Lithium profile have any 'Float' component? Or is it simply 50A up until the threshold voltage is reached and then Zero current? Knowing
Victron this will be customisable no doubt but I wondered how
Victron chose their default LFP setting.
Ta
Best thing to do is install the VictronConnect App, run that up and select "Orion XS" from the Demo Library and you can see what the defaults are and what is changable.
) a 
. So once I get a few rest days I'll be trying to fit it to our van, and no doubt be asking for help again with the wiring in etc. Thank you all for your help so far. 
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